Keeping soft water fish in very hard water?

[Lavender]

So, I’m planning a 75 gallon filled to the brim with tetras, kuhli loaches, a female betta (Sprinkles), and some other soft-water fish. Big problem is, my tap water is liquid rock- 7.5 ph, but the GH…it’s literally off the chart of the little test tube. Now, I’ve heard that normally this isn’t a problem, but I’m wary, as when my dad tried to keep tetras, they all died. ONLY his tetras. Everything else was fine. While I will do a RODI system if I have to, I’ve realized it’s going to add around 300 bucks in total to my aquarium price.
 

I know normally PH and GH don’t matter. But..I am quite wary. The tank was old, and he can’t remember how he kept it, so it could have been husbandry. It could have also been that they were neon tetras. They died slowly over 3-4 days every time he got them. Do I need the RODI system, or can I leave it?

[Kurt Brutting]

Stable parameters are key. I know some breeders who keep pretty acidic fish in pretty alkaline water. As long as your not having major parameter shifts you should be good to go. Seasoned aquariums come with time and parameters stay in place. Set it up and just give it time to balance and then season and slowly add fish over time. 
 

[Sora]

On 8/18/2023 at 8:44 PM, Lavender said:

female betta (Sprinkles), and some other soft-water fish. Big problem is, my tap water is liquid rock- 7.5 ph, but the GH…it’s literally off the chart of the little test tube

I don’t know if this helps, but I have a female betta with very hard water 160ppm ish (Idk haven’t checked in a while) . And she’s doing very well, stability is key.

[nabokovfan87]

On 8/18/2023 at 5:44 PM, Lavender said:

I know normally PH and GH don’t matter. But..I am quite wary.

https://www.aquariumcoop.com/blogs/aquarium/ph-gh-kh

So I think the confusion here is PH specifically isn't the real concern.  What matters, in my experience, is KH and GH.  PH is treated similar to TDS as sort of a number without real meaning for me.  If water is stagnant (no oxygenation) the PH can shift based on that parameter.  If water is full of co2, low oxygen, that also can shift the PH.  Once you have that in your tank and you have the oxygenation adequate you will (and should) see the PH shift.  Part of this is the process of off-gassing.  So even though your tap is PH of whatever number, KH is actually a bit more informative as to what the normal PH value would be.  In my case I have a PH from the tap around 6.8-7.0, KH is around 3 degrees.  I can boost my KH up to ~4 degrees and things remain stable for me and hold that PH.  As mentioned in the ACO blog article, KH is a bit tied into the organic matter in the tank.  Organics will use up that KH and drop your PH as a result. 

I apologize if all of that seems very complex, but I just wanted to clarify that what you really should be concerned with is the KH range that is acceptable for the fish as well as your KH in your aquarium/tap.

The most common way to lower PH/KH for harder water is to use active substrate, aquarium soil, which will absorb KH and then drop that KH value.  The plants can use those ions and then you have a more acidic water parameter for the tank than when you started.  Over time this stabilizes as the soil itself "fills up" with all the KH/GH  ions.  You replenish them via water changes.  This is a common technique used for keeping caridina species and wild caught fish that need those lowered parameters.  The issue long term is that in order to keep the KH/PH low you need to find a way of reducing it long term from the tap.  RO or Distilled water is the main method people use and then they add the KH they need back in with buffering powders.

I think another real world example is something cory outlines in this video.  It's a bit of a longer explanation, but I promise you the video is extremely informative and you will learn from the discussion on the topic of keeping tetra fish and their sourcing.
 

As mentioned above, stability is absolutely the key.  That being said KH/PH does matter in some circumstances.  My amano shrimp don't like to go above 7.6 or they turn bright red and have issues.  Same with my corydoras.  I've seen it happen.  I've seen softwater fish have issues in hard water because I just did not understand enough when purchasing them.  Acclimation methods, tank stability, it's all related and leads to a healthy fish, long term. 

We're all hear to help and we all have our own experiences and knowledge to bring to the conversation.  It's a great community and it's so awesome to be able to have interesting conversation like this about the animals we care for!

[Guppysnail]

My tap is 8.2-8.4 after it’s gassed off. My gh is over 300. I kept a male betta and neon tetras they lived happy lives. 
 

I set the tank up and allowed it to season as others suggested. As it settled in and seasoned the tank ph slowly lowered to 7.6-7.8. 
 

I did small weekly water changes to keep the parameters stable instead of large ones. If I ran into situations where nitrates were getting too high I would do 2 small water changes that week. 
 

Folks above gave you great advice I just wanted to share my experience to help set your mind at ease a bit. 

[JChristophersAdventures]

@Lavender I would consider other alternatives before spending a lot of money on an RO system.

Even fish caught from the wild in softer water have usually gone through several completely different sets if water parameters by the time they reach the consumer, and tank bred tetras, for example, my never have seen significantly soft water like yours. Really, as fish keepers, we would benefit greatly from knowing all that, but we rarely do. Fortunately, if we source healthy fish to start with, acclimate (and/or quarantine) them slowly, and keep the parameters steady in a properly cycled tank... then, over-all, we will be successful with very few bumps in the road.

The reason I am pointing this out, is that your Dad had over-all success with your local water. RO would completely throw that out-the-window and give you completely different water. Maybe, what you need to do is keep the otherwise sound water and simply bring down the GH to reasonable levels.

Here are some practical ways you can do this:

(1) Source tank bred tetras you know were raised in harder water (they are usually hardier than wild caught, anyway).

(2) use a water soften pillow (bag) to absorb excess calcium and magnesium (the basis of high GH). API makes these, they are relatively cheap (under $10), they are effective over time and can be "recharged" in an aquarium salt bath (with two, you just keep one charging while using the other). These are designed to be used in a canister filter or med to larger HOBs. There may be a way to use them with a sponge filter, but I a not sure about that.

(3) add substantial driftwood decor (Malaysian driftwood would be my choice if I was trying to soften the water) and there are other plant material/leaves that can also modify your excessive GH as well (yes, your PH and KH can be effected as well, but it is better to work toward a better balanced water using more gradual/natural means if possible).

Why? Is it too much trouble? I think it is worth trying. Here's why:

Once you go the RO route, your costs are just beginning. (1) You will need to maintain and change the RO filters as they don't last forever (at least once a year, as I understand it) and that's not cheap. (2) You would also have to "fix" the RO water by re-adding the minerals etc that you need... using Equilibrium or another similar product whenever you replace significant amounts of your water. That's another expense. And, how will the other fish you will keep react to completely different water? We don't know.

I would certainly look into these things (maybe you already have) before spending $300 as opposed to a couple of API pillows, a bucket and some aquarium salt (to recharge them... you may already have a lot of this stuff on-hand) and some driftwood/specialty leaves.

Just some thoughts. Hope that helps.